Within the next two weeks, he will be anointed one of the most powerful men in the world. Xi Jinping, 59, a tall and genial figure who has risen through the ranks of the Chinese Communist Party, is to be selected as its new leader in a once-in-a-decade congress that will transfer power to a new generation.

When, next year, he formally becomes China's president he will take charge of a country with a 1.3 billion population - more than four times that of the USA - that's expanding so fast it grows an economy the size of Greece every three months.

As he takes over from President Hu Jintao, he will become responsible for the world's largest armed forces, with 2.3 million serving men and women, up to 400 nuclear warheads, nearly 1,000 naval vessels and more than 5,000 aircraft.

Yet for years Mr Xi he was less well-known than his wife, Peng Liyuan, a glamorous folk-singer and one of China's most popular performers. And even today, after more than 10 years in senior party positions and five years as a member of the ruling politburo, he remains an enigma.

A privileged Communist party "princeling", he was once banished to the countryside for seven years; he is an official who made his name by high profile attacks on corruption, yet some of his relations have been linked to wealth amassed through their connections.

Mr Xi is an apparently open-minded traveller with a daughter at Harvard, but he once harangued "bored foreigners, with full stomachs, who have nothing better to do than point fingers at us".

Unpicking the story of his life is not made easier by the fact that his official biography - spanning years of turmoil within China - has been repeatedly delayed as bureaucrats haggle over what it should include.

To discover more about Mr Xi and his origins, The Sunday Telegraph visited three key locations in his own and his family's past - a story that began in Yan'an, in northwest China, in 1935, as the Communists struggled to seize power.

Here Mr Xi's father, Xi Zhongxun, a revolutionary fighter, helped shelter Mao Zedong and other Communist party leaders fleeing the Chinese nationalist army - bringing to an end their famous "Long March".

For months they lived among some of the poorest people in China, in traditional cave houses - buildings with brick fronts whose interiors are scooped out of the soft rock of steeply sloping hillsides.

Today's Yan'an is a beacon for Red Tourism, with thousands of Chinese coming through daily to view the place where the Party has its roots.

As the communists' eventually fought their way to power, Xi Zhongxun moved to Beijing where in 1952 he became head of the party's propaganda machine - just nine months before his son Xi Jinping, the third of four children, was born. He then progressed further, becoming a vice premier.

But amid the poisonous political climate of China under Chairman Mao in the 1960s, Xi Zhongzun was accused of leading an anti-party clique. First he was banished to a remote tractor factory for five years; then, as the Cultural Revolution erupted in 1968, he was jailed.

Xi Jinping, aged just 16, was sent to the countryside to work with farmers, exchanging familiar Beijing for a dusty and impoverished rural area - near where Mao had once been sheltered by his father - in pursuit of ideals which he later admitted, in an interview with state-run television, had "proved an illusion".

In the village of Liangjiahe, Mr Xi spent seven years of great hardship, living in spartan cave houses carved from the mountainside and working among the peasants.

That village was firmly off limits when The Sunday Telegraph visited, with local officials and police chasing off outsiders and warning elderly residents not to speak to them - and surrounding the house of one man who is known to recall Mr Xi from those days.

By all accounts this period had a deep personal impact on Mr Xi. His father was eventually rehabilitated but once recalled how his children barely recognised him when they were finally reunited.

Mr Xi himself learned to hate ideological struggles. In an essay published in 2003, he wrote, "Much of my pragmatic thinking took root back then, and still exerts a constant influence on me."

Others, too, recall how tough that time was for Mr Xi. Some 200 miles south is Zhonghe, a sleepy village of about 60 families who live in old-fashioned mud, brick and wooden farmhouses set amidst vast fields of corn in Fuping county.

This is where Mr Xi's father was brought up, part of a landowning family, before he left and joined the Red Army. And here his cousin Ding Fengqin, 70, welcomed The Sunday Telegraph into the courtyard of the modest Xi family home as she recalled how, in the late 1960s, a teenaged Mr Xi turned up to ask for help.

"He was exiled to Yan'an in the summer, and he didn't have cotton-padded clothes for winter, so he came here. My brother and his wife asked a tailor to make cotton-padded clothes for him," she said.

The expected elevation of Mr Xi has brought sudden attention to this town, which has been officially designated his ancestral home.

"Lots of people come here to see us already," said Mrs Ding. "There's nothing to see here as we are poor. We have no furniture for daily use, we don't have luxury chairs or tables either, just shabby houses. We'll need to tear down this house and renovate soon."

But Mr Xi visited only occasionally as he made his way to the centre of power. After several attempts to join the Communist party, he was finally accepted as a member in 1975 and moved back from the countryside to Beijing, to study chemical engineering at Tsinghua University, widely seen as one of the best in China.

His father was eventually released and, his reputation restored, quickly resumed positions of power, introducing key reforms including an early experiment in liberalising China's economy. He also used his influence to help Mr Xi ascend the Communist Party ladder.

From his first lowly official position in Beijing in 1979, he steadily moved up government ranks, following the well-trodden path of long spells in the regions. It was during this time that he took part in a visit to the small town of Muscatine, Iowa, to study farming techniques - to which he returned during an official visit to the US this year. Locals remember him as polite, kind and devoted to his work.

As vice mayor of Xiamen, a coastal city of Fujian province, he too introduced economic reforms and encouraged investment from Taiwan, and eventually became governor of the province - but was fortunate to escape with his career intact, after a prominent local businessman was implicated in a huge corruption and smuggling scandal.

Among part officials who quizzed Mr Xi over that in 2000 was then vice president Hu Jintao - the man whom Mr Xi will succeed next month.

Perhaps Mr Xi impressed Mr Hu because he appeared himself to be following a strict regime. Li Shih-Wei, a Taiwanese businessman who worked with Mr Xi at the time said that lunch and dinner meetings were usually held in the government cafeteria, not opulent restaurants. "He didn't lead a luxurious lifestyle," he told The Washington Post, adding: "His working efficiency was pretty high. That's pretty rare among the officials we met here."

Mr Li said that Mr Xi did not like even the appearance of impropriety. When a group of businessmen once offered to pay a social call on Mr Xi at home, he declined, saying: "Business is done in the office."

Mr Xi spent much of the next decade as party boss in Zhejiang province, another coastal region, where he helped deliver 14 per cent growth and took a high-profile line against corruption.

In one of a series of local newspaper columns, he complained about officials who display "the haughty manner of feudalism". Mr Xi wrote: "If we stay removed from ordinary people, we will be like a tree cut off from its roots. Officials at all levels should change their working style, get close to ordinary people, try their best to do good things for people, put down the haughty manner and set a good example for ordinary people."

When the mayor of Shanghai was brought down over allegations that he had used up to one third of the city's £1 billion pension pot to pay for roads and property development - eventually to be jailed for 18 years - Mr Xi was drafted in as party chief, his final stepping stone to power in Beijing.

In 2007 he was elected to the nine-man politburo and put in charge of preparations for the Olympics - a success that dramatically raised China's international profile and confirmed his own standing within the leadership.

Yet, for all that, he was little known by most people until he was elevated to the post of vice president that same year - a sign that he was being groomed of as Hu Jintao's likely successor.

Far better known for most of his career was his wife Miss Peng, 50, a major-general who as one of the country's best-known folk singers heads the song and dance troupe of the People's Liberation Army. "When he comes home, I've never felt as if there's some leader in the house. In my eyes, he's just my husband," she once told an interviewer.

The couple has a daughter, Xi Mingze, who is studying under a pseudonym at Harvard University - the same institution attended until June by Bo Guagua, the son of disgraced communist party chief Bo Xilai.

Quite how Mr Xi will fare on the international stage is hard to gauge. His concluded his outburst against foreigners, delivered he thought in private to an audience of Chinese businessmen abroad, by declaring: "China does not, first, export revolution; second, export poverty and hunger; third, cause troubles for you. What else is there to say?"

But it may not be typical: foreign leaders he has met have generally been impressed and Henry Kissinger, the former US secretary of state who engineered America's first serious diplomatic overtures to China, is convinced that Mr Xi will also seek huge internal changes to how the country is governed.

Back in Fuping, deep in China's heartland, there is no doubt what his leadership means. Long before Xi Jinping takes power, his legacy is being constructed to mark what is officially being declared as his family hometown.

A six-lane roadway cuts, still only half built, through the fields near Mr Xi's father's childhood home, its ultimate destination a nearly finished four-storey shopping and entertainment complex.

"When Xi Jinping becomes the president, many people will want to come here and see this place, because it's where his father lived," said Gao Yuming, 36, a construction worker building the road to the shopping complex.

And Mrs Ding spoke proudly both of the cousin for whom she had once helped hunt out warm clothes, and of his revolutionary father, who died in 2002. "Xi (Jinping) looks a little like his father, though his eyes are not as big," she said.

"Their personalities are also alike. They don't talk much. The family's men are all modest and prudent.

She was surprised and thrilled three years ago when Peng Liyuan arrived at the door, unannounced, for a half-hour visit to her husband's family. But Mr Xi himself had not visited for some years, she said, and she did not expect he would do while he was president.

"He's worked step-by-step to achieve this. He's got talent," she said. "He will not come back, that's certain. He can't come back now."